Studies described in this proposal are designed to investigate the control mechanisms involved in the activation of chondrocytes by products of inflammation and the role of this process in the degradation and repair of cartilage matrix. A cell culture model has been established employing human articular chondrocytes in monolayer culture as target cells for the action of a soluble product from cultured human blood mononuclear cells, mononuclear cell factor (MCF), which stimulates the production of prostaglandins and neutral proteases. I plan to characterize further this cellular interaction, using collagen synthesis as a measure of matrix repair and plasminogen activator as a measure of degradation. Human chondorcyte cultures in agarose matrix will be established and it will be determined whether these cells are capable of being activated by MCF under these conditions. The types of collagen synthesized in agarose compared with monolayer cultures will be characterized and the effects of MCF on type II vs. type I collagen synthesis will be studied. I intend to continue studies of the control of plasminogen activator in chondrocyte cultures comparing cell-associated with released activity and to characterize further an inhibitor of serine proteasses, protease nexin, whose release by chondrocytes is stimulated by MCF. Cell-free translation of mRNA from MCF-stimulated chondrocytes will be employed to study the levels of translatable RNA for specific chondorcyte proteins. The control of the production of type I and type II collagens at the transcriptional level will be studied using specific human collagen cDNA probes. Finally, these studies will lead eventually to investigation of the permissive role of growth and attachment factors in chondrocyte synthetic functions.